Treating ferrous sheets and plates



' Patented July 12, 1932 UNITED STATES PATENT OFFICE HARRY S. SCHUTTE, OF PITTSBUBGH, .,PENNSYLVANI.A

TREATING EEBROTUS SHEETS AND PLATES No Drawing.

ing, 'is essential because the pile of sheets or plates have become welded together or adherent in varying the heat treatment to which the piles are subjected in such annealing operations. And the same difficulties are encountered but to alesser extent in box annealing cold rolled materials.

After the annealing operation it is necessary for each sheet to be freed from any temporary union with the others of the pile so as to be ready for subsequent processing or use. While all of the sheets or plates in an annealing charge are not usually stuck together in the manner indicated, such condition is present to a Very considerable extent 3O rolled material andto a degree in annealed piles of cold rolled materials. The result is that the slow, laborious and costly process of manually opening a pile of annealed'materials has heretofore been a regular and unescapa'ble feature of the mill routine.

The primary object of this invention is the provision of improved means whereby the objectionable welding or sticking together of the sheets and plates ordinarily present after the box annealing operation is prevented or, to a large extent, overcome, and the labor necessary in opening the materials in readiness for cold rolling and further treatment isreduced to a minimum; likewise,.the reduction in and prevention of rust formation and substantial elimination of the destructive stain-. in g of the surfaces of the sheets or plates generally present in the methods used heretodegrees while undergoing which the sheets or plates to be treated are in practically every annealed pile of hot Application filed m 31, 1930. Serial No. 472,186.

fore, are effected in a simple, rapid and economical manner.

Still further objects of theinvention will be made apparent hereinafter in the detailed description and appended claims. In the practice of the improved method the sheets or plates, after the removal of the scale and prior to annealing, are treated by dipping them in a suitable aqueous mixture or chemical solution, preferably a solution of sodium bichromate or sodium chromate.

W1th existing tin mill equipment it is possible to provide for the. bichromate treatment by adding the chemical in proper proportions to the rinse or Wash tank at the pickler. A M concentration of"0.05 per cent. sodium bichromate or of sodium chromate in the wash water has been found suflicient to accomplish the desired results. Thus, the sheets or plates, as soon as the oxid or scale has been removed by the action of the pickling operation, are. immersed, rinsed and treated in a dilute solution of sodium bichromate or sodium chromate, after which they are in- 5 spected in theusual manner and arranged in piles for the black annealing operation.

' A more economical and eifective method 'is to provide an additional dipping tank, in

immersed in the solution or aqueous mix-' ture after having been rinsed with water in the wash tank.

Whatever portion of the solution or mixture adheres to the sheets or plates as they are formed into piles on the charging stands is usually allowed to remain on the surfaces.

It has been found that this treatment practically eliminates troublesome stickin or welding of the sheets or plates in the su sequent annealing process; that better anneal ing is obtained; that the annealing temperature can be raised at least 100 degrees Fahrenheit; that the opening operation is greatly facilitated and that the spoilage of many 95 sheets or plates in the opening operation is avoided. A reduction of approximately 50 per cent. in the cost 'of opening is thus effected.

chromate or analogous treatment is a material reduction in the amount of destructive staining on the surfaces of the materials which heretofore has contributed to the production of defective tin coatings.

The action of rust on the pickled materials while still wet apparently is retarded and in this Way contributesto a better. surface condition.

The'term aqueous mixture as used herein is intended to cover any of the chemical solutions or mixtures specified 'as usable in practicing my invention.

While sodium bichromate is the best material found so far in accomplishing the results. described above I have found that other materials likewise have beneficial efi'ects. Other chromates and bichromates may be used. Potassium bichromate, of course, will give similar results, having properties similar to those of sodium bichromate. The broad idea underlying this invention is in that the presence of a separating or reacting medium, extremely thin, and particularly a substance which in itself wouldmilitate against physical welding or sticking of the rolled material, will be beneficial.

While the fundamental concept lies in the use of a separating medium between sheets in a box annealing operation one important feature was to find the materials of greatest efliciency which, at the same time, would not by their presence interfere with subsequent operations. Various chemical salts, oxidizing agents and compounds have beenused to good effect in the place of bichromate; for example, the chromates and among others are zinc sulphate, sodium permanganate, zinc chloride and/or zinc oxide, all of which have desirable properties in relation to this process.

In designating a concentration of 0.05 per cent. sodium bichromate as satisfactory I have given this figure only as being representative of the approximate minimum desirable in one particular embodiment of the invention.

Higher concentrations may be maintained and the manner of application of the solution may be modified so that it will fit into any procedure for the production of rolled ferrous metal plates and the like. Concentrations as low as 0.001 per cent. have been found to give beneficial results.

The advantages of my invention will be apparent to those skilled in the art. The materials used in forming the aqueous mixture with which the sheets and plates are treated are not limited to those specifically mentioned herein and other changes may be made within the scope of the invention, as defined by the claims.

I claim:

1. The method of preventing sticking in box annealing sheets and plates which consists in chemically treating the rolled and plckled sheets and plates by immersion in an aqueous solution of sodium bichromate of a concentration of .05 per cent., piling the treated materials and then box annealing the pile.

2. The method of preventing sticking in box annealing sheets and plates which consists in chemically treating the rolled and pickled sheets and plates by immersion in an aqueous solution of sodium bichromate of a concentration of .03 to .05 per cent, piling the treated materials and then box annealing the ile. p 3. The method of preventing sticking in box annealing'sheets and plates which consists in chemically treating the rolled and pickled sheets or plates by immersion in an aqueous solution of a sodium salt of a chromic acid of aconcentration of .001 to .20 per cent., piling the treated materials and then box annealing the pile.

4E. The method of preventing sticking in box annealing sheets and plates which consists in chemically treating the rolled and pickled sheets and plates by immersion in an aqueous solution of a salt of a chromic acid of a concentration of .001 to .20 per cent, piling the treated materials and then box annealing the pile. I

In testimony whereof, I have hereunto set my hand.

HARRY S. SCHUTTE. 

